Upper-tropospheric Jet Research Articles

Using Causal Effect Networks to Analyze Different Arctic Drivers of Midlatitude Winter Circulation

AbstractIn recent years, the Northern Hemisphere midlatitudes have suffered from severe winters like the extreme 2012/13 winter in the eastern United States. These cold spells were linked to a meandering upper-tropospheric jet stream pattern and a negative Arctic Oscillation index (AO). However, the nature of the drivers behind these circulation patterns remains controversial. Various studies have proposed different mechanisms related to changes in the Arctic, most of them related to a reduction in sea ice concentrations or increasing Eurasian snow cover.Here, a novel type of time series analysis, called causal effect networks (CEN), based on graphical models is introduced to assess causal relationships and their time delays between different processes. The effect of different Arctic actors on winter circulation on weekly to monthly time scales is studied, and robust network patterns are found. Barents and Kara sea ice concentrations are detected to be important external drivers of the midlatitude circulation, influencing winter AO via tropospheric mechanisms and through processes involving the stratosphere. Eurasia snow cover is also detected to have a causal effect on sea level pressure in Asia, but its exact role on AO remains unclear. The CEN approach presented in this study overcomes some difficulties in interpreting correlation analyses, complements model experiments for testing hypotheses involving teleconnections, and can be used to assess their validity. The findings confirm that sea ice concentrations in autumn in the Barents and Kara Seas are an important driver of winter circulation in the midlatitudes.

Quantifying isentropic stratosphere‐troposphere exchange of ozone

AbstractThere is increased evidence that stratosphere‐troposphere exchange (STE) of ozone has a significant impact on tropospheric chemistry and radiation. Traditional diagnostics of STE consider the ozone budget in the lowermost stratosphere (LMS) as a whole. However, this can only render the hemispherically integrated ozone flux and therefore does not distinguish the exchange of ozone into low latitudes from that into high latitudes. The exchange of ozone at different latitudes may have different tropospheric impacts. This present study extends the traditional approach from the entire LMS to individual isentropic layers in the LMS and therefore gives the meridional distribution of STE by the latitudes where each isentropic surface intersects the tropopause. The specified dynamics version of the Whole Atmosphere Community Climate Model is used to estimate the STE ozone flux on each isentropic surface. It is found that net troposphere‐to‐stratosphere ozone transport occurs in low latitudes along the 350–380 K isentropic surfaces and that net stratosphere‐to‐troposphere ozone transport takes place in the extratropics along the 280–350 K isentropes. Particularly, the seasonal cycle of extratropical STE ozone flux in the Northern Hemisphere displays a maximum in late spring and early summer, following the seasonal migration of the upper tropospheric jet and associated isentropic mixing. Furthermore, differential diabatic heating and isentropic mixing tend to induce STE ozone fluxes in opposite directions, but the net effect results in a spatiotemporal pattern similar to the STE ozone flux associated with isentropic mixing.

북서태평양 원격패턴에 의한 북서태평양 태풍활동에서의 변화

Abstract This study analyzes the characteristics of Western North Pacific (WNP) tropical cyclone (TC) activity and large-scale environments according to the Western Pacific (WP) teleconnection pattern in summer. In the positive WP phase, an anomalous cyclone and an anomalous anticyclone develop in the low and middle latitudes of the East Asia, respectively. As a result, southeasterlies are reinforced in the northeast area of the East Asia including Korea and Japan which facilitates the movement of TC to this area, whereas northwesterlies are reinforced in the southwest area of the East Asia including South China and Indochina Peninsula which blocks the movement of TC to this area. Due to the spatial distribution of this reinforced pressure system, TCs develop, move, and turn more to the northeast of WNP than those in the negative WP phase. Consequently, the characteristics of this TC activity in the positive WP phase are associated with the location of upper tropospheric jet further to the northeast. Meanwhile, TCs in the negative WP phase mainly move to the west from Philippines toward south China and Indochina Peninsula. Furthermore, due to the terrain effect caused by the high passage frequency of TCs in the mainland China, the intensity of TCs are weaker than those in the positive WP phase.Key words:Western Pacific teleconnection pattern, Tropical cyclone, Large-scale environments, East Asia, Upper tropospheric jet

Revisiting the second EOF mode of interannual variation in summer rainfall over East China

The second EOF (EOF2) mode of interannual variation in summer rainfall over East China is characterized by inverse rainfall changes between South China (SC) and the Yellow River–Huaihe River valleys (YH). However, understanding of the EOF2 mode is still limited. In this study, the authors identify that the EOF2 mode physically depicts the latitudinal variation of the climatological summer-mean rainy belt along the Yangtze River valley (YRRB), based on a 160-station rainfall dataset in China for the period 1951–2011. The latitudinal variation of the YRRB is mostly attributed to two different rainfall patterns: one reflects the seesaw (SS) rainfall changes between the YH and SC (SS pattern), and the other features rainfall anomalies concentrated in SC only (SC pattern). Corresponding to a southward shift of the YRRB, the SS pattern, with above-normal rainfall in SC and below-normal rainfall in the YH, is related to a cyclonic anomaly centered over the SC–East China Sea region, with a northerly anomaly blowing from the YH to SC; while the SC pattern, with above-normal rainfall in SC, is related to an anticyclonic anomaly over the western North Pacific (WNP), corresponding to an enhanced southwest monsoon over SC. The cyclonic anomaly, related to the SS pattern, is induced by a near-barotropic eastward propagating wave train along the Asian upper-tropospheric westerly jet, originating from the mid–high latitudes of the North Atlantic. The anticyclonic anomaly, for the SC pattern, is related to suppressed rainfall in the WNP.

Toward the Dynamical Convergence on the Jet Stream in Aquaplanet AGCMs

Abstract Systematic sensitivity of the jet position and intensity to horizontal model resolution is identified in several aquaplanet AGCMs, with the coarser resolution producing a more equatorward eddy-driven jet and a stronger upper-tropospheric jet intensity. As the resolution of the models increases to 50 km or finer, the jet position and intensity show signs of convergence within each model group. The mechanism for this convergence behavior is investigated using a hybrid Eulerian–Lagrangian finite-amplitude wave activity budget developed for the upper-tropospheric absolute vorticity. The results suggest that the poleward shift of the eddy-driven jet with higher resolution can be attributed to the smaller effective diffusivity of the model in the midlatitudes that allows more wave activity to survive the dissipation and to reach the subtropical critical latitude for wave breaking. The enhanced subtropical wave breaking and associated irreversible vorticity mixing act to maintain a more poleward peak of the vorticity gradient, and thus a more poleward jet. Being overdissipative, the coarse-resolution AGCMs misrepresent the nuanced nonlinear aspect of the midlatitude eddy–mean flow interaction, giving rise to the equatorward bias of the eddy-driven jet. In accordance with the asymptotic behavior of effective diffusivity of Batchelor turbulence in the large Peclet number limit, the upper-tropospheric effective diffusivity of the aquaplanet AGCMs displays signs of convergence in the midlatitude toward a value of approximately 107 m2 s−1 for the ∇2 diffusion. This provides a dynamical underpinning for the convergence of the jet stream observed in these AGCMs at high resolution.

Tropical origin for the impacts of the Atlantic Multidecadal Variability on the Euro-Atlantic climate

Atlantic Multidecadal Variability (AMV) is known for influencing the mid-latitude climate variability, especially over the European region. This letter assesses the impact of the wintertime AMV in a group of 200-year atmospheric-only numerical experiments, in which the atmosphere is forced with positive and negative AMV-like sea surface temperatures (SSTs) and sea ice concentration patterns. Anomalies are applied separately to the whole North Atlantic ocean, to the extratropics (north of 30° N) and to the tropics (between 0° and 30° N). Results show that AMV anomalies considerably affect the North Atlantic Oscillation (NAO), the jet stream variability and the frequency of atmospheric blocking over the Euro-Atlantic sector, resulting in a negative (positive) NAO during positive (negative) AMV. It is found that the bulk of the signal is originated in the tropics and it is associated with a Gill-like response—an anomalous upper tropospheric streamfunction dipole over the tropical Atlantic driven by the SST anomalies—and with the subsequent structural change of the upper-tropospheric jet, which affects the propagation of Rossby waves in the North Atlantic. Conversely, the NAO response is almost negligible when the AMV anomalies are applied only to the extratropics, suggesting that the relevance of SST anomalies along the North Atlantic frontal zone may be overestimated.

Aircraft measurements of gravity waves in the upper troposphere and lower stratosphere during the START08 field experiment

Abstract. This study analyzes in situ airborne measurements from the 2008 Stratosphere–Troposphere Analyses of Regional Transport (START08) experiment to characterize gravity waves in the extratropical upper troposphere and lower stratosphere (ExUTLS). The focus is on the second research flight (RF02), which took place on 21–22 April 2008. This was the first airborne mission dedicated to probing gravity waves associated with strong upper-tropospheric jet–front systems. Based on spectral and wavelet analyses of the in situ observations, along with a diagnosis of the polarization relationships, clear signals of mesoscale variations with wavelengths ~ 50–500 km are found in almost every segment of the 8 h flight, which took place mostly in the lower stratosphere. The aircraft sampled a wide range of background conditions including the region near the jet core, the jet exit and over the Rocky Mountains with clear evidence of vertically propagating gravity waves of along-track wavelength between 100 and 120 km. The power spectra of the horizontal velocity components and potential temperature for the scale approximately between ~ 8 and ~ 256 km display an approximate −5/3 power law in agreement with past studies on aircraft measurements, while the fluctuations roll over to a −3 power law for the scale approximately between ~ 0.5 and ~ 8 km (except when this part of the spectrum is activated, as recorded clearly by one of the flight segments). However, at least part of the high-frequency signals with sampled periods of ~ 20–~ 60 s and wavelengths of ~ 5–~ 15 km might be due to intrinsic observational errors in the aircraft measurements, even though the possibilities that these fluctuations may be due to other physical phenomena (e.g., nonlinear dynamics, shear instability and/or turbulence) cannot be completely ruled out.

Seasonal Predictability of Extratropical Storm Tracks in GFDL’s High-Resolution Climate Prediction Model

Abstract The seasonal predictability of extratropical storm tracks in the Geophysical Fluid Dynamics Laboratory’s (GFDL)’s high-resolution climate model has been investigated using an average predictability time analysis. The leading predictable components of extratropical storm tracks are the ENSO-related spatial patterns for both boreal winter and summer, and the second predictable components are mostly due to changes in external radiative forcing and multidecadal oceanic variability. These two predictable components for both seasons show significant correlation skill for all leads from 0 to 9 months, while the skill of predicting the boreal winter storm track is consistently higher than that of the austral winter. The predictable components of extratropical storm tracks are dynamically consistent with the predictable components of the upper troposphere jet flow for both seasons. Over the region with strong storm-track signals in North America, the model is able to predict the changes in statistics of extremes connected to storm-track changes (e.g., extreme low and high sea level pressure and extreme 2-m air temperature) in response to different ENSO phases. These results point toward the possibility of providing skillful seasonal predictions of the statistics of extratropical extremes over land using high-resolution coupled models.

A simple climatology of westerly jet streams in global reanalysis datasets part 1: mid-latitude upper tropospheric jets

A simple closed contour object identification scheme has been applied to the zonal mean monthly mean zonal wind fields from nine global reanalysis data sets for 31 years of the satellite era (1979–2009) to identify objects corresponding to westerly jet streams. The results cluster naturally into six individual jet streams but only the mid-latitude upper-tropospheric jets are considered here. The time series of the jet properties from all reanalyses are decomposed into seasonal means and anomalies, and correlations between variables are evaluated, with the aim of identifying robust features which can form the basis of evaluation metrics for climate model simulations of the twentieth century. There is substantial agreement between all the reanalyses for all jet properties although there are some systematic differences with particular data sets. Some of the results from the object identification applied to the reanalyses are used in a simple example of a model evaluation score for the zonal mean jet seasonal cycle.

Effect of high-frequency wind on intraseasonal SST variabilities over the mid-latitude North Pacific region during boreal summer

The effect of high-frequency (period <20 days) wind on the intraseasonal (period 20–100 days) sea surface temperature (SST) anomalies over the mid-latitude North Pacific region (35°–45°N, 160°E–170°W) during boreal summer was examined through the diagnosis of reanalysis data and numerical experiments. The reanalysis data diagnosis shows that the near-surface high-frequency (HF) wind is weaker (stronger) during the intraseasonal SST warming (cooling) phase. The phase-dependent amplitude of HF wind is controled by the strength change of the upper-tropospheric westerly jet stream. Because the magnitude of the HF wind over the target region shows significantly positive correlation with the total wind speed, a weaker (higher) HF wind in the SST warming (cooling) phase tends to decrease (increase) total wind speed, which can further suppress (enhance) upward surface latent heat and sensible heat fluxes and strengthen the intraseasonal SST variability. The numerical experiments with an oceanic general circulation model demonstrate that the HF wind can amplify the intraseasonal SST variability over the target region mainly through nonlinearly rectifying intraseasonal surface latent and sensible heat fluxes. The HF wind can explain about 20 % of the intraseasonal SST variability in the target region.

The Relevance of the Location of Blocking Highs for Stratospheric Variability in a Changing Climate

Abstract Previous research shows that blocking highs (BHs) influence wintertime polar stratospheric variability through the modulation of the climatological planetary waves (PWs) depending on the BH location. BHs over the Euro-Atlantic sector tend to enhance the upward PW propagation, and those over the northwestern Pacific Ocean tend to reduce it. Future changes are examined in the response of the wave activity flux to the BH location and their relationship with wintertime stratospheric variability in transient simulations of ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC). After it is verified that EMAC can reproduce qualitatively well the geographical dependence of the BH influence on PW activity injection, it is shown that this dependence does not change in the future. However, an eastward shift of the pattern of the BH influence on PW propagation over the Pacific, a farther eastward extension of the pattern over the Atlantic Ocean, and an intensification of the wavenumber-1 component of the interaction between climatological and anomalous waves are detected. Changes in the upper-tropospheric jet and an intensification of the wavenumber-1 climatological wave due to a strengthening of the Aleutian low agree with these variations. The spatial distribution of future BHs preceding extreme polar vortex events is also affected by the slight modifications in the wave activity pattern. Hence, future BHs preceding strong vortex events tend to be more concentrated over the Pacific than in the past, where BHs interfere negatively with wavenumber-1 climatological waves. Future BHs prior to major stratospheric warmings are located in a broader area than in the past, predominantly over an extended Euro-Atlantic sector.

Kinetic Energy Budget of a Tropical Cyclone

An analysis of the kinetic energy budget is made for a tropical cyclone. Horizontal flux convergence constitutes a major energy source. Generation of kinetic energy via cross-contour flow is a persistent sink throughout the pre-storm and growth periods. Dissipation of kinetic energy from subgrid to grid scales is an important source during the pre-storm and growth periods; it acts as the major sink of energy during the decay period. The major contribution to kinetic energy comes from a persistent upper tropospheric jet stream activity throughout the period of the cyclone development. Unlike midlatitude cyclones, a considerable quantity of kinetic energy appears between 850 - 500 hPa layers especially during the growth period. While the behavior of the values of horizontal divergence by nondivergent wind closely resemble to those of total horizontal divergence term, neglecting the divergent part of the wind would clearly lead to a considerable error in the calculation of total horizontal divergence. The mean error in approximation of total horizontal divergence by the nondivergent part during the life cycle of our cyclone is about 36%.

Rainy-Season Precipitation over the Sichuan Basin and Adjacent Regions in Southwestern China

Abstract The spatial variability and diurnal propagation of mean precipitation in the summer rainy seasons (from 2003 to 2010) over the Sichuan basin (SCB) and adjacent mountainous regions are examined using high spatiotemporal resolution satellite-derived precipitation estimates. The SCB is located just east of the Tibetan Plateau (TP) and is prone to heavy precipitation that often peaks over nighttime and early morning. The large-scale environment over the SCB during the rainy season is characterized by weak low- to midtropospheric convergence in the lee of the TP and by the upper-tropospheric jet stream to the north. Under this flow configuration, the study links the unique diurnal variations in the precipitation pattern and propagation to the unique topography in this region. It is found that during the rainy season, the local diurnal precipitation maximum moves primarily downslope and southeastward, from over the TP in the daytime to SCB at night. A secondary maximum moves northeastward downslope of the Yunnan–Guizhou Plateau toward the SCB from late evening to the early morning. The movement of precipitation over the SCB and the adjacent regions is closely tied to multiple regional-scale mountain–plain solenoids because of the large contrast in terrain heights between the basin and surrounding mountain ranges.

Wintertime cyclone/anticyclone activity over China and its relation to upper tropospheric jets

In this study, the wintertime cyclone/anticyclone activity and its variability over China are examined based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data from 1948 to 2007. The climatology of the source, path and lysis regions for cyclones/anticyclones is investigated using an automatic tracking algorithm. Apparent asymmetries in source, lysis and path regions are observed between cyclones and anticyclones.The 1948–2007 data exhibit an upward trend in the annual number and a downward trend in the cyclone and anticyclone intensity. The leading empirical orthogonal function (EOF) mode of the cyclone transit counts (CTC) for the 1948–2007 period indicates an increase in cyclone activity over northeastern East Asia since the late 1970s that becomes significant in the mid-1980s. The first EOF mode of the anticyclone transit counts (ATC) is a monopole over northern East Asia, centred west of Lake Baikal, which has increased since 1970. The CTC variability dominates the ATC variability, which corresponds well with the storm track variability.Two distinct variability modes in the upper tropospheric jets over East Asia are also observed. The first mode describes an oscillation in the subtropical jet position; the second mode describes the polar-front jet strength variation. Moreover, the second mode is closely linked to the cyclone/anticyclone activity variability.

Thunderstorms enhance tropospheric ozone by wrapping and shedding stratospheric air

AbstractA significant source of ozone in the troposphere is transport from the stratosphere. The stratospheric contribution has been estimated mainly using global models that attribute the transport process largely to the global‐scale Brewer‐Dobson circulation and synoptic‐scale dynamics associated with upper tropospheric jet streams. We report observations from research aircraft that reveal additional transport of ozone‐rich stratospheric air downward into the upper troposphere by a leading‐line‐trailing‐stratiform mesoscale convective system with convection overshooting the tropopause altitude. The fine‐scale transport demonstrated by these observations poses a significant challenge to global models that currently do not resolve storm‐scale dynamics. Thus, the upper tropospheric ozone budget simulated by global chemistry‐climate models where large‐scale dynamics and photochemical production from lightning‐produced NO are the controlling factors may require modification.

Short vertical-wavelength inertia-gravity waves generated by a jet–front system at Arctic latitudes – VHF radar, radiosondes and numerical modelling

Abstract. Inertia-gravity waves with very short vertical wavelength (λz≤1000 m) are a very common feature of the lowermost stratosphere as observed by the 52 MHz radar ESRAD (Esrange MST radar) in northern Scandinavia (67.88° N, 21.10° E). The waves are seen most clearly in radar-derived profiles of buoyancy frequency (N). Here, we present a case study of typical waves from 21 February to 22 February 2007. Good agreement between N2 derived from radiosondes and by radar shows the validity of the radar determination of N2. Large-amplitude wave signatures in N2 are clearly observed by the radar and the radiosondes in the lowermost stratosphere, from 9 km to 14–16 km height. Vertical profiles of horizontal wind components and potential temperature from the radiosondes show the same waves. Mesoscale simulations with the Weather Research and Forecasting (WRF) model are carried out to complement the analysis of the waves. Good agreement between the radar and radiosonde measurements and the model (except for the wave amplitude) shows that the model gives realistic results and that the waves are closely associated to the upper-level front in an upper-troposphere jet–front system. Hodographs of the wind fluctuations from the radiosondes and model data show that the waves propagate upward in the lower stratosphere confirming that the origin of the waves is in the troposphere. The observations and modelling all indicate vertical wavelengths of 700 ± 200 m. The radiosonde hodograms indicate horizontal wavelengths between 40 and 110 km and intrinsic periods between 6 and 9 h. The wave amplitudes indicated by the model are however an order of magnitude less than in the observations. Finally, we show that the profiles of N2 measured by the radar can be used to estimate wave amplitudes, horizontal wavelengths, intrinsic periods and momentum fluxes which are consistent with the estimates from the radiosondes.

On the Dynamics, Thermodynamics, and Forecast Model Evaluation of Two Snow-Burst Events in Southern Alberta

Abstract Two high-impact convective snowband events (“snow bursts”) that affected Calgary, Alberta, Canada, are examined to better understand the dynamics and thermodynamics of heavy snowbands not associated with lake effects or the cold conveyor belt of synoptic-scale cyclones. Such events are typically characterized by brief, but heavy, periods of snow; low visibilities; and substantial hazards to automobile and aviation interests. Previous literature on these events has been limited to a few case studies across North America, including near the leeside foothills of the U.S. Rockies. The large-scale dynamics and thermodynamics are investigated using the National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR). Previously, high-resolution convection-explicit Weather Research and Forecasting Model (WRF) simulations have shown some ability to successfully reproduce the dynamics, thermodynamics, and appearance of convective snowbands, with small errors in location and timing. Therefore, WRF simulations are performed for both events, and are evaluated along with the NCEP North American Mesoscale (NAM) model forecasts. Both the NARR and WRF simulations show that while the two snow bursts are similar in appearance, they form as a result of different dynamic and thermodynamic mechanisms. The first event occurs downstream of an upper-tropospheric jet streak in a region of little synoptic-scale ascent, where ageostrophic frontogenesis helps to release conditional, dry symmetric, and inertial instability in an unsaturated environment. The inertial instability is determined to be related to fast flow over upstream high terrain. The second event occurs in a saturated environment in a region of Q-vector convergence (primarily geostrophic frontogenesis), which acts to release conditional, convective, and conditional symmetric instability (CSI).

Climatology of Upper Tropospheric–Lower Stratospheric (UTLS) Jets and Tropopauses in MERRA

Abstract A global climatology (1979–2012) from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) shows distributions and seasonal evolution of upper tropospheric jets and their relationships to the stratospheric subvortex and multiple tropopauses. The overall climatological patterns of upper tropospheric jets confirm those seen in previous studies, indicating accurate representation of jet stream dynamics in MERRA. The analysis shows a Northern Hemisphere (NH) upper tropospheric jet stretching nearly zonally from the mid-Atlantic across Africa and Asia. In winter–spring, this jet splits over the eastern Pacific, merges again over eastern North America, and then shifts poleward over the North Atlantic. The jets associated with tropical circulations are also captured, with upper tropospheric westerlies demarking cyclonic flow downstream from the Australian and Asian monsoon anticyclones and associated easterly jets. Multiple tropopauses associated with the thermal tropopause “break” commonly extend poleward from the subtropical upper tropospheric jet. In Southern Hemisphere (SH) summer, the tropopause break, along with a poleward-stretching secondary tropopause, often occurs across the tropical westerly jet downstream of the Australian monsoon region. SH high-latitude multiple tropopauses, nearly ubiquitous in June–July, are associated with the unique polar winter thermal structure. High-latitude multiple tropopauses in NH fall–winter are, however, sometimes associated with poleward-shifted upper tropospheric jets. The SH subvortex jet extends down near the level of the subtropical jet core in winter and spring. Most SH subvortex jets merge with an upper tropospheric jet between May and December; although much less persistent than in the SH, merged NH subvortex jets are common between November and April.

Distinct modes of East Asian Winter Monsoon documented by a southern Red Sea coral record

The large-scale boreal winter climatic patterns associated with interannual variability in a coral oxygen isotope (δ18O) record from the southern Red Sea covering most of the last century are investigated. From the early 1930s to the early 1960s, the winter coral δ18O record, reflecting temperature and salinity variations in southern Red Sea surface waters, is associated with global (or large scale) sea surface temperature (SST) and 850 mb geopotential height (Z850) anomalies which project on the corresponding patterns associated with the El Nino-Southern Oscillation (ENSO). In contrast, since the early 1960s the winter coral δ18O record is related to a Z850 pattern that reflects the ENSO-independent part of the East Asian Winter Monsoon (EAWM), which includes the Siberian High, the East Asian through, and the East Asian upper-tropospheric Jet. Our results indicate a weakening of the ENSO control on interannual temperature/salinity variations in southern Red Sea surface waters in the early 1960s, due to the warming of the Indian Ocean, and suggest that information about the nonstationarity in the relationship between ENSO and two distinct modes of EAWM can be documented in southern Red Sea coral δ18O records.

The Development and Evolution of Two Atmospheric Rivers in Proximity to Western North Pacific Tropical Cyclones in October 2010

AbstractThis study investigates the evolution of two zonally elongated atmospheric rivers (ARs) that produced &amp;gt;200 mm of rainfall over mountainous regions of Northern California in late October 2010. Synoptic-scale analysis and air parcel trajectory analysis indicate that the ARs developed within high-CAPE environments characterized by troposphere-deep ascent as water vapor was transported directly from western North Pacific tropical cyclones (TCs) toward the equatorward entrance region of an intensifying North Pacific jet stream (NPJ). The same ARs were subsequently maintained as water vapor was transported from extratropical and subtropical regions over the central and eastern North Pacific in an environment characterized by quasigeostrophic forcing for ascent and strong frontogenesis along the anticyclonic shear side of an intense and zonally extended NPJ. Although the ARs developed in conjunction with water vapor transported from regions near TCs and in the presence of troposphere-deep ascent, an atmospheric water vapor budget illustrates that decreases in integrated water vapor (IWV) via precipitation are largely offset by the horizontal aggregation of water vapor along the AR corridors via IWV flux convergence in the presence of frontogenesis. The frameworks used for investigations of predecessor rain events ahead of TCs and of interactions between recurving TCs and the NPJ are also utilized to illustrate many dynamically similar processes related to AR development and evolution. Similarities include the following: water vapor transport directly from a TC, troposphere-deep ascent in a high-CAPE environment beneath the equatorward entrance region of an intensifying upper-tropospheric jet streak, interactions between diabatic outflow and an upper-tropospheric jet streak, and strong frontogenesis.